Positives

• In the Norwegian CycloME open-label phase II study, 55% of ME/CFS patients responded to six IV cyclophosphamide infusions, with SF-36 Physical Function rising from 35.0 to 69.5 in responders and 68% of responders still in remission at four-year follow-up Frontiers.
  
  
• Patients positive for HLA-DQB1*03:03 or HLA-C*07:04 had an 83% response rate, suggesting genetic typing may identify subsets most likely to benefit PubMed.
  
  

Negatives

• The CycloME trial excluded very severe bedbound ME patients and lacked a placebo control, so the chemotherapy benefit cannot be cleanly separated from natural fluctuation PLOS.
  
  

Hurdles & Side Effects

• Cyclophosphamide is an oncology chemotherapy agent with risks of infertility, bone marrow suppression, hemorrhagic cystitis, and secondary cancers, and outside the Norwegian research setting it is essentially impossible to access for ME/CFS or Long COVID Me-Pedia.